The present invention relates to a quantum effect device and the like used for super-integration of an electronic circuit.
The semiconductor industry has achieved a high degree of integration by reducing an area occupied by one functional element and developed together with improvements on technologies, for example, of a process, an element, circuit design and the like to achieve such a high degree of integration.
As a switching element used for switching in a semiconductor chip, while a MOS transistor has mainly employed, control of a diffused layer formed in an Si substrate has been harder and in addition improvement on reliability of an isolation oxide film has been problematic since the transistor is operated by applying an electric field to an interface with progress in miniaturization of an element. Particularly, in connection with the reliability of an isolation oxide film, it has been widely known that a trap level caused by an impurity, a defect and the like in the oxide film and a high electric field encourage tunneling of electrons and generate a leakage current.
Under such circumstances, although efforts have been conducted to improve a film quality at a molecular level in order to solve the problem, it has not sufficiently been understood how to improve the film quality and therefore, it is hard to improve a film quality at a molecular level in a semiconductor fabrication process under the current technologies, so that it is considered that the improvement is rather impossible. Further, since a semiconductor substrate which is uniform in structure and in composition has been employed, it is difficult to fabricate various devices in one chip.
For such reasons, a functional element, which has a margin in film quality, whose switching function is not deteriorated even with the presence of a some leakage current, and which has no diffused layer has been required. In detail, it is required to provide a function element, which operates at a low voltage of 1V or lower, and which can make a current drastically larger than a leakage current flow in a conductive condition or a circuit device which uses a semiconductor composite substrate and various kinds of converter, and which can process an optical signal, an analogue signal, a digital signal and the like at the same time.